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Abstract:

The present invention relates to an image generating apparatus (1) which
comprises a plurality of image generating optical paths (P1, P2, P3) and
single and common means (30) for simultaneously deflecting a received
plurality of light beams (l1, l2, l3) of primary illumination light (L1)
having coherence properties. Said light beams (l1, l2, l3) are assigned
to said respective optical paths (P1, P2, P3). Said single common means
(10) for deflecting is configured in order to simultaneously optically
couple each of said received light beams (l1, l2, l3) into a respective
assigned optical path (P1, P2, P3) and in order to irradiate intermediate
faces (21, 21-1, 21-2, 21-3; S, S1, S2, S3) of illumination units (20,
20-1, 20-2, 20-3) of each respective optical path (P1, P2, P3) with said
respective assigned light beam (l1, l2, l3) as well as an order to
have--during said process of irradiating--each of said beams (l1, l2, l3)
subsequently in time irradiate different portions of said respective
assigned intermediate faces (21, 21-1, 21-2, 21-3; S, S1, S2, S3).

Claims:

1. Image generating apparatus (1),comprising a plurality of three image
generating optical paths (P1, P2, P3), each of said image generating
optical paths (P1, P2, P3) having a respective intermediate face (21,
21-1, 2'-2, 21-3; S, S1, S2, S3), andcomprising a sweep mirror (11) as
single means (10)--common for said plurality of optical paths (P1, P2,
P3)--for simultaneously deflecting a received plurality of light beams
(l1, l2, l3) of primary illumination light (L1) having coherence
properties, each of said light beams (l1, l2, l3) being assigned to a
respective one of said optical paths (P1, P2, P3), for being tilted in
one or two dimensions,wherein each optical path (P1, P2, P3)
comprises:respective three image generating panel (31-1, 31-2, 31-3) as
respective means (30, 30-1, 30-2, 30-3) for generating a respective
partial images (I, I-1, I-2, I-3), each of said three image generating
panels (31-1, 31-2, 31-3) for displaying a partial image (I1, I2, I3) in
the primary colours red, green, and blue respectively, andrespective
illumination optical means as respective means (20, 20-1, 20-2, 20-3) for
illuminating said respective means (30, 30-1, 30-2, 30-3) for generating
said respective partial image (I, I1, I2, I3), each means (20, 20-1,
20-2, 20-3) for illuminating having said respective intermediate face
(21, 21-1, 21-2, 21-3; S, S1, S2, S3), each of said respective
illumination optical means modify respective beams (11, 12, 13) of light
in order to illuminate a respective panel (31-1, 31-2, 31-3) uniformly
and with a beam shape being congruent to the shape of the respective
panel (31-1, 31-2, 31-3),wherein said single and common means (10) for
deflecting is configured in order to simultaneously optically couple each
of said received light beams (l1, l2, l3) into a respective assigned
optical path (P1, P2, P3) and to thereby simultaneously irradiate each of
said intermediate faces (21, 21-1, 21-2, 21-3; S, S1, S2, S3) with a
respective one assigned light beam (l1, l2, l3),wherein said single and
common means (10) for deflecting is configured in order to have--during
said process of irradiating and by being tilted--each of said light beams
(l1, l2, l3) by reflecting said light beams (l1, l2, l3) into common or
different directions, dependent on the angle of incidence subsequently in
time irradiate different portions of said respective assigned
intermediate face (21, 21-1, 21-2, 21-3; S, S1, S2, S3) by sweeping each
of said respective light beams (l1, l2, l3) across a respective
intermediate face (21, 21-1, 21-2, 21-3; S, S1, S2, S3),further
comprising a projection lens (PL) as means (40) for projecting said
partial images (I1, I2, I3) received from said respective means (30-1,
30-2, 30-3) for generating said partial images (I1, I2, I3), which
projects the partial images (I1, I2, I3) displayed on the respective
panels (31-1, 31-2, 31-3),wherein said means (40) for projecting said
partial images (I1, I2, I3) has an aperture stop (41, AS), andwherein
each one of said intermediate faces face (21, 21-1, 21-2, 21-3; S, S1,
S2, S3) of said respective means (20, 20-1, 20-2, 20-3) for illuminating
is positioned in optical conjugation with respect to said aperture stop
(41, AS),further comprising three laser light sources (l1, l2, l3) for
emitting light of said respective primary colours and comprising optical
means for converging respective light beams (l1, l2, l3) at common or
different angles of incidence to a common point or region at said sweep
mirror (11), andfurther comprising means (43) for combining said light
beans (l1, l2, l3) of said primary colours emitted from said respective
panels (31-1, 31-2, 31-3) into a common optical path.

2. Image generating apparatus (1) according to claim 1,wherein two laser
light sources (l1, l2) are combined into a common optical path,wherein
said common optical path for said two laser light sources (l1, l2) and
the single optical path for the remaining laser light source (l3) are
converged under different angles of incidence at a common point or region
of said sweep mirror (11) and reflected into different directions,
dependent on the angle of incidence,wherein one common illumination unit
(20-1) is provided for the common optical path and one illumination unit
(20-2) is provided for the single optical path, andwherein an X-cube or
cross-prism is provided for combining the red, green, and blue light of
the partial images (I1, I2, I3) into a common optical path.

4. Apparatus (1) according to any one of the preceding claims,wherein said
single and common means (10) for deflecting is adapted in order to have
during said process of irradiating said intermediate faces (21, 21-1,
21-2, 21-3; S, S1, S2, S3) each of said light beams (11, 12, 13) take
consecutively in time different positions on said respective assigned
intermediate face (21, 21-1, 21-2, 21-3; S, S1, S2, S3).

5. Apparatus (1) according to any one of the preceding claims,wherein said
single and common means (10) for deflecting is adapted in order to have
during said process of irradiating said intermediate faces (21, 21-1,
21-2, 21-3; S, S1, S2, S3) each of said light beams (l1, l2, l3) sweep
across said respective assigned intermediate face (21, 21-1, 21-2, 21-3;
S, S1, S2, S3).

6. Apparatus (1) according to any one of the preceding claims,wherein said
single common means (10) for deflecting is adapted in order to have
during said process of irradiating said intermediate face (21, 21-1,
21-2, 21-3; S, S1, S2. S3) each of said light beams (l1, l2, l3)
continuously move across said respective intermediate face (21, 21-1,
21-2, 21-3; S, S1, S2, S3).

7. Apparatus (1) according to any one of the preceding claims,wherein said
intermediate face (21, 21-1, 21-2, 21-3; S, S1, S2, S3) is a surface of
said respective means (20, 20-1, 20-2, 20-3) for illuminating.

8. Apparatus (1) according to any one of the preceding claims,wherein said
intermediate face (21.21-1, 21-2, 21-3; S, S1, S2, S3) is an interface of
said means (20, 20-1, 20-2, 20-3) for illuminating.

9. Apparatus (1) according to any one of the preceding claims,wherein said
intermediate face (21, 21-1, 21-2, 21-3; S, S1, S2, S3) is a virtual
plane of said means (20, 20-1, 20-2, 20-3) for illuminating.

10. Apparatus (1) according to any one of the preceding claims,wherein
said intermediate face (21, 21-1, 21-2, 21-3; S, S1, S2, S3) is a face of
a diffuser (22) of said means (20, 20-1, 20-2, 20-3) for illuminating.

11. Apparatus (1) according to any one of the preceding claims,further
comprising means (50) for generating primary illumination light (L1)
which is focussed to a focal plane,wherein said means (10) for deflecting
is positioned in said focal plane.

12. Apparatus (1) according to any one of the preceding claims, wherein
said means (40) for projecting comprises means (43) for receiving said
partial images (I1, I2, I3) and for combining said partial images (I1,
I2, I3) into a combined image (I).

13. Apparatus (1) according to any one of the preceding claims,wherein
said means (10) for deflecting is or comprises a mirror (11).

14. Apparatus (1) according to claim 13,wherein said mirror (11) is
adapted for being mechanically tilted in order to thereby deflect each of
said received light beams (l1, l2, l3) across said respective assigned
intermediate face (21, 21-1, 21-2, 21-3; S, S1, S2, S3).

15. Apparatus (1) according to any one of the preceding claims 13 or
14,wherein said mirror (11) is adapted in order to have each of said
deflected light beams (11, 12, 13) move across said respective assigned
intermediate face (21, 21-1, 21-2, 21-3; S, S1, S2, S3) in one of a
circular manner, a linear manner, cyclical manner and chaotic manner.

16. Apparatus (1) according to any one of the preceding claims,further
comprising means (50) for generating primary illumination light (L1)
which is adapted in order to direct said primary illumination light (L1)
to said means (10) for deflecting said primary illumination light (L1).

17. Apparatus (1) according to claim 16,wherein said means for generating
primary illumination light (L1) has an according plurality of laser light
sources (51-1, 51-2, 51-3).

18. Apparatus (1) according to any one of the preceding claims 16 or
17,wherein said means (50) for generating primary illumination light (L1)
has an according plurality of arrays of laser light sources (51-1, 51-2,
51-3) which are adapted in order to generate and direct respective arrays
of laser light beams (l1, l2, l3) to said means (10) for deflecting said
primary illumination light (L1).

19. Apparatus (1) according to any one of the preceding claims,wherein
each of said means (30, 30-1, 30-2, 30-3) for generating a partial image
(I1, I2, I3) is or comprises a respective image modulator (LCD1, LCD2.
LCD3).

20. Apparatus (1) according to any one of the preceding claims,wherein
each of said means (30, 30-1, 30-2, 30-3) for generating a partial image
(I1, I2, I3) is or comprises at least one respective liquid crystal
display element.

21. Apparatus (1) according to any one of the preceding claims,wherein
each of said means (20, 20-1, 20-2, 20-3) for illuminating is or
comprises an illumination unit.

22. Apparatus (1) according to any one of the preceding claims,wherein for
the plurality of image generating optical paths (P1, P2, P3) single first
collimation optics (23-1) is provided common for said plurality of image
generating optical paths (P1, P2, P3).

23. Apparatus (1) according to any one of the preceding claims,wherein a
light pipe is provided configured to illuminate respective means (30) for
generating an image.

24. Apparatus (1) according to any one of the preceding claims,wherein a
rectangular beam diffuser is provided in the optical path to illuminate
respective means (30) for generating an image.

25. Image generating apparatus (1),comprising a plurality of image
generating optical paths (P1, P2, P3), each of said image generating
optical paths (P1, P2, P3) having a respective intermediate face (21,
21-1, 21-2, 21-3; S, S1, S2, S3), andcomprising single means (10)--common
for said plurality of optical paths (P1, P2, P3)--for simultaneously
deflecting a received plurality of light beams (l1, l2, l3) of primary
illumination light (L1) having coherence properties, each of said light
beams (l1, l2, l3) being assigned to a respective one of said optical
paths (P1, P2, P3),wherein said single and common means (10) for
deflecting is configured in order to simultaneously optically couple each
of said received light beams (l1, l2, l3) into a respective assigned
optical path (P1, P2, P3) and to thereby simultaneously irradiate each of
said intermediate faces (21, 21-1, 21-2, 21-3; S, S1, S2, S3) with a
respective one assigned light beam (l1, l2, l3), andwherein said single
and common means (10) for deflecting is configured in order to
have--during said process of irradiating--each of said light beams (l1,
l2, l3) subsequently in time irradiate different portions of said
respective assigned intermediate face (21, 21-1, 21-2, 21-3; S, S1, S2,
S3).

Description:

FIELD OF THE INVENTION

[0001]The present invention relates to an image generating apparatus and
in particular a projection apparatus using laser light sources and more
particular to a RGB laser projector with improved image quality.

BACKGROUND OF THE INVENTION

[0002]Nowadays apparatuses and devices for generating images and for
projecting the same as well as their miniaturization become more and more
important in many customer devices and electronic appliances. The problem
of such apparatuses and devices--in particular when using light sources
which at least to some extent produce or at least involve coherent
light--is that in the process of image generation and image projection
the produced images contain noise and other inhomogenities which are due
to the coherent nature of the involved light. These inhomogenities are in
part in particular caused by interference processes at optical faces,
surfaces or interfaces. The noise component is usually called speckle and
is generated majorly by interference processes, for instance at diffusing
faces or interfaces, e.g. at diffusing screens.

[0003]These circumstances are also given when using a plurality of
different light sources having coherence properties and having different
spectral properties, e.g. different colours.

SUMMARY OF THE INVENTION

[0004]It is therefore an object underlying the present invention to
provide an image generating apparatus which is capable of at least
reducing the content of inhomogenities and speckle in the produced images
and which has at the same time a more compact structure.

[0005]The object underlying the present invention is solved by an image
generating apparatus according to claims 1 and 3. Embodiments and
modifications of the image generating apparatus according to the present
invention are within the scope of the dependent claims.

[0006]According to one aspect of the present invention an image generating
apparatus is provided. Said image generating apparatus comprises a
plurality of image generating optical paths each of said image generating
optical paths having a respective intermediate face and single
means--common for said plurality of optical paths--for simultaneously
deflecting a received plurality of light beams of primary illumination
light having coherence properties, each of said light beams being
assigned to a respective one of said optical paths, wherein said single
and common means for deflecting is configured in order to simultaneously
optically couple each of said received light beams into a respective
assigned optical path and to thereby simultaneously irradiate each of
said intermediate faces with a respective one assigned light beam, and
wherein said single and common means for deflecting is configured in
order to have--during said process of irradiating--each of said light
beams subsequently in time irradiate different portions of said
respective assigned intermediate face.

[0007]It is therefore on the one hand one aspect of the present invention
to provide said means for deflecting said received light beams of primary
illumination light having coherence properties with the functionality to
have said deflected light beams of primary illumination light
subsequently irradiate different portions of an assigned intermediate
face of an assigned means for illuminating. As a consequence as time
progresses the differently illuminated portions of the respective
assigned intermediate faces which are well used for image generation at
least to some extent loose their coherency property and are therefore to
some extent incoherent with respect to each other as there exist and
appear at different time instances. Therefore because of the lost of
coherency--they cannot contribute to the speckle phenomenon anymore.

[0008]It is, on the other hand, an aspect of the present invention to
realize a comparable compact structure for an image generating apparatus
which uses a plurality of different image generating optical paths. This
is achieved by providing said means for deflecting said received light
beams of primary illumination light having coherence properties as a
common means for deflecting--common for the entire plurality of optical
paths and with the functionality to have each of said deflected light
beams of primary illumination light simultaneously enter one respective
optical path assigned thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]The invention will now be explained based on preferred embodiments
thereof and by taking reference to the accompanying and schematical
figures.

[0010]FIG. 1 is a schematic block diagram for elucidating some basic
aspects of an embodiment of the image generating apparatus according to
the present invention.

[0011]FIG. 2 is a schematic and perspective side view for elucidating some
basic aspects of another embodiment of an image generating apparatus
according to the present invention elucidating more constructive details
thereof.

[0012]FIG. 3 is a schematic view demonstrating key ideas of an embodiment
of an image generating apparatus according to the present invention.

[0013]FIGS. 4A-C are schematic and cross-sectional side views of further
embodiments of an image generating apparatus according to the present
invention.

[0014]FIG. 5 is a schematic and cross-sectional side view of a common
image generating apparatus.

DETAILED DESCRIPTION OF THE INVENTION

[0015]In the following functional and structural similar or equivalent
element structures will be denoted with the same reference symbols. Not
in each case of their occurrence a detailed description will be repeated.

[0016]At first, in the following reference is taken to the Figs. in
general:

[0017]According to one aspect of the present invention said image
generating apparatus 1 is proposed, comprising a plurality of three image
generating optical paths P1, P2, P3, each of said image generating
optical paths P1, P2, P3 having a respective intermediate face 21, 21-1,
21-2, 21-3; S, S1, S2, S3, and comprising a sweep mirror 11 as single
means 10--common for said plurality of optical paths P1, P2, P3--for
simultaneously deflecting a received plurality of light beams l1, l2, l3
of primary illumination light L1 having coherence properties, each of
said light beams l1, l2, l3 being assigned to a respective one of said
optical paths P1, P2, P3, for being deflected in one or two dimensions,
wherein each optical path P1, P2, P3 comprises respective three image
generating panel 31-1, 31-2, 31-3 as respective means 30, 30-1, 30-2,
30-3 for generating a respective partial images I, I-1, I-2, I-3, each of
said three image generating panels 31-1, 31-2, 31-3 for displaying a
partial image I1, I2, I3 in the primary colours red, green, and blue
respectively, and respective illumination optical means as respective
means 20, 20-1, 20-2, 20-3 for illuminating said respective means 30,
30-1, 30-2, 30-3 for generating said respective partial image I, I1, I2,
I3, each means 20, 20-1, 20-2, 20-3 for illuminating having said
respective intermediate face 21, 21-1, 21-2, 21-3; S, S1, S2, S3, each of
said respective illumination optical means modify respective beams l1,
l2, l3 of light in order to illuminate a respective panel 31-1, 31-2,
31-3 uniformly and with a beam shape being congruent to the shape of the
respective panel 31-1, 31-2, 31-3, wherein said single and common means
10 for deflecting is configured in order to simultaneously optically
couple each of said received light beams l1, l2, l3 into a respective
assigned optical path P1, P2, P3 and to thereby simultaneously irradiate
each of said intermediate faces 21, 21-1, 21-2, 21-3; S, S1, S2, S3 with
a respective one assigned light beam l1, l2, l3, wherein said single and
common means 10 for deflecting is configured in order to have--during
said process of irradiating and by being tilted--each of said light beams
l1, l2, l3 by reflecting said light beams l1, l2, l3 into common or
different directions, dependent on the angle of incidence subsequently in
time irradiate different portions of said respective assigned
intermediate face 21, 21-1, 21-2, 21-3; S, S1, S2, S3 by sweeping each of
said respective light beams l1, l2, l3 across a respective intermediate
face 21, 21-1, 21-2, 21-3; S, S1, S2, S3, further comprising a projection
lens PL as means 40 for projecting said partial images I1, I2, I3
received from said respective means 30-1, 30-2, 30-3 for generating said
partial images I1, I2, I3, which projects the partial images I1, I2, I3
displayed on the respective panels 31-1, 31-2, 31-3, wherein said means
40 for projecting said partial images I1, I2, I3 has an aperture stop 41,
AS, and wherein each one of said intermediate faces face 21, 21-1, 21-2,
21-3; S, S1, S2, S3 of said respective means 20, 20-1, 20-2, 20-3 for
illuminating is positioned in optical conjugation with respect to said
aperture stop 41, AS, further comprising three laser light sources l1,
l2, l3 for emitting light of said respective primary colours and
comprising means for converging respective light beams l1, l2, l3 at
common or different angles of incidence to a common point or region at
said sweep mirror 11, and further comprising means 43 for combining said
light beans l1, l2, l3 of said primary colours emitted from said
respective panels 31-1, 31-2, 31-3 into a common optical path.

[0018]In addition, in the proposed Image generating apparatus 1 two laser
light sources l1, l2 may be combined Into a common optical path, said
common optical path for said two laser light sources l1, l2 and the
single optical path for the remaining laser light source 13 may be
converged under different angles of incidence at a common point or region
of said sweep mirror 11 and reflected into different directions,
dependent on the angle of incidence, one common illumination unit 20-1
may be provided for the common optical path and one illumination unit
20-2 may be provided for the single optical path, and an X-cube or
cross-prism may be provided for combining the red, green, and blue light
of the partial images I1, I2, I3 into a common optical path.

[0019]According to one aspect of the present invention said image
generating apparatus 1 may comprise a plurality of image generating
optical paths P1, P2, P3, each of said image generating optical paths P1,
P2, P3 having a respective intermediate face 21, 21-1, 21-2, 21-3; S, S1,
S2, S3, and also may comprise single means 10--common for said plurality
of optical paths P1, P2, P3--for simultaneously deflecting a received
plurality of light beams l1, l2, l3 of primary illumination light L1
having coherence properties, each of said light beams l1, l2, l3 being
assigned to a respective one of said optical paths P1, P2, P3, wherein
said single and common means 10 for deflecting is configured in order to
simultaneously optically couple each of said received light beams l1, l2,
l3 into a respective assigned optical path P1, P2, P3 and to thereby
simultaneously irradiate each of said intermediate faces 21, 21-1, 21-2,
21-3; S, S1, S2, S3 with a respective one assigned light beam l1, l2, l3,
and wherein said single and common means 10 for deflecting is configured
in order to have--during said process of irradiating--each of said light
beams l1, l2, l3 subsequently in time irradiate different portions of
said respective assigned intermediate face 21, 21-1, 21-2, 21-3; S, S1,
S2, S3.

[0022]Said single and common means 10 for deflecting may be adapted in
order to have during said process of irradiating said intermediate faces
21, 21-1, 21-2, 21-3; S, S1, S2, S3 each of said light beams l1, l2, l3
take sequentially or consecutively in time different positions on said
respective assigned intermediate face 21, 21-1, 21-2, 21-3; S, S1, S2,
S3.

[0023]Said single and common means 10 for deflecting may be adapted in
order to have during said process of irradiating said intermediate faces
21, 21-1, 21-2, 21-3; S, S1, S2, S3 each of said light beams l1, l2, l3
sweep across said respective assigned intermediate face 21, 21-1, 21-2,
21-3; S, S1, S2, S3.

[0024]Said single common means 10 for deflecting may be adapted in order
to have during said process of irradiating said intermediate face 21,
21-1, 21-2, 21-3; S, S1, S2, S3 each of said light beams l1, l2, l3
continuously move across said respective intermediate face 21, 21-1,
21-2, 21-3; S, S1, S2, S3.

[0033]Said means 10 for deflecting may be or may comprise a mirror 11.

[0034]Said mirror 11 may be adapted for being mechanically tilted in order
to thereby deflect each of said received light beams l1, l2, l3 across
said respective assigned intermediate face 21, 21-1, 21-2, 21-3; S, S1,
S2, S3.

[0035]Said mirror 11 may be adapted in order to have each of said
deflected light beams l1, l2, l3 move across said respective assigned
intermediate face 21, 21-1, 21-2, 21-3; S, S1, S2, S3 in one of a
circular manner, a linear manner, cyclical manner and chaotic manner.

[0036]Said image generating apparatus 1 may further comprise means 50 for
generating primary illumination light L1 which is adapted in order to
direct said primary illumination light L1 to said means 10 for deflecting
said primary illumination light L1.

[0038]Said means 50 for generating primary illumination light L1 may have
an according plurality of arrays of laser light sources 51-1, 51-2, 51-3
which are adapted in order to generate and direct respective arrays of
laser light beams 11, 12, 13 to said means 10 for deflecting said primary
illumination light L1.

[0039]Each of said means 30, 30-1, 30-2, 30-3 for generating a partial
image I1, I2, I3 may be or may comprise a respective image modulator
LCD1, LCD2, LCD3.

[0040]Each of said means 30, 30-1, 30-2, 30-3 for generating a partial
image I1, I2, I3 may be or may comprise at least one respective liquid
crystal display element LCD1, LCD2, LCD3.

[0047]It is proposed to provide an optical module to be used in projectors
incorporating micro displays and enlarging optics to generate images on a
screen.

[0048]As light source multiple lasers of different wavelengths are used to
generate coloured images. To avoid image artefacts caused by interference
structures introduced by the coherency of light and periodic structures
of the optical elements, a special beam sweeping part is used in
combination with illumination optic.

[0049]The optical system includes a beam sweeping element and is a compact
and low cost solution for an optical illumination system based on laser
light sources.

[0050]Micro display based projection systems, especially systems with
reflective micro displays, like LCoS (Liquid Crystal on Silicon) are well
known for many years. The arrangement of displays around the polarizing
beam splitting cubes and colour recombination cube is a kind of standard
architecture used in LCoS based projection systems: see FIG. 5.

[0051]Known projectors are working with high pressure discharge lamps on
mercury or xenon basis. The white spectrum of the lamp is divided into
separate wavelength regions and then each wavelengths region is modulated
by a single imager responsible for the wavelength portion. Usually 3
imagers are used: one for green, one for blue and one for red.

[0052]Taking three laser light sources, e.g. red, green and blue, to
illuminate three displays would require three illumination paths adapted
to the laser light sources. This would increase the size and cost of the
projector. Further speckle reduction techniques had to be implemented
into three illumination channels, which further increases cost.

[0053]Our system shows how to minimize and simplify illumination optics,
by keeping system compactness and the advantages of laser light sources.

[0054]Laser light sources supply already discrete wavelengths, for
instance R (red), G (green) and B (blue). Projectors using laser light
sources therefore need no wavelength separation. The problem here is to
find a good compromise between the benefit of already separated colours
and the compactness of the illumination system.

[0056]Following description is related to the invented optical
architecture using red, blue and green laser light sources for
illumination of micro displays, and projecting the image content onto a
screen.

[0057]The illumination arrangement as an image generating apparatus--an
embodiment thereof is shown in FIG. 4A--is also called optical engine and
consists of two main parts. The first part consists of the above
mentioned three laser light sources, a sweep mirror or rotating mirror, a
collimation lens and optional two diffusers. The second part consists of
an arrangement of two illumination units (here: two pairs of lens arrays,
two condenser lenses) and one dichroic mirror for colour splitting.

[0058]Further, in the second part, an arrangement of three polarizing beam
splitter cubes (PBS) attached around a colour recombination cube is
provided. At the light entrance section of the PBS, field lenses are
placed to provide reflective micro displays with telecentric
illumination. The three reflective micro displays placed in such a way
that the incoming s polarized light is first reflected by the PBS onto
the micro display. The micro displays modulate the light and reflect it
in direction to the colour recombination cube.

[0059]Description of the working principle, starting with the first part
of optical engine: A red, a green and a blue laser light source is used,
where each laser light sources can emit either a single beam or an array
of laser beams. The laser light sources are arranged in a way that the
beams from two lasers are combined into a common optical path by use of
an dichroic mirror. The beam of the third laser is separated, having
different optical path. In the following text these beams are called
combined beam and single beam, respectively. The combined and single
beams are arranged around the sweep mirror in that way that both paths
are converging under a different angle directly onto the mirror.
Additional lenses can be used before the sweep mirror in order to focus
each beam or array of beams onto the sweep mirror and to form a small
spot at the sweep mirror, even if the laser beams consist of an extended
array of sub-beams. The combined and the single beam are reflected at the
sweep under different angles. A collimation lens is placed in such a
position, that the sweep mirror is at the focal point of the collimation
lens. Therefore both the combined and the single beam are collimated
after the collimation lens and parallel to each other.

[0060]The sweep mirror can tilt a few degrees in one or two dimensions
around a static pivot, which lies in the focal point of the collimation
lens. With the movement of the sweep mirror both the combined and the
single beam sweep across the entrance section of the illumination units,
thereby reducing speckle noise. The movement should be fast enough to
avoid flickering.

Description of the Second Part of Illumination Optics:

[0061]The illumination units will generate a uniform and rectangular light
distribution at the micro display. This configuration is standard in most
of the LCD projectors. Only difference here is that we are using two
illumination paths, one for the single beam and the other for the
combined beam.

[0062]In the optical path of combined beam we have put a dichroic mirror
to split the combined beam in to its two discrete wavelengths again to
illuminate the micro displays with their required colour.

[0063]After light is modulated by each of the three micro displays the
modulated light is guided to the colour recombination cube to combine all
three colours and to project a full coloured picture onto the screen.

[0064]The proposed system has an increased image quality, by reducing
interference pattern and speckle without loosing throughput efficiency.

[0065]According to a further aspect a very compact architecture for
illuminating three micro displays, each with a discrete wavelength from a
laser source, is demonstrated. It is more compact compared to combining
all three laser beams into one beam, having one common speckle reducing
illumination unit, but then again splitting the light into three discrete
optical paths in order to illuminate the micro displays.

[0066]Still according to a further aspect the proposed arrangement is more
compact than illuminating each micro display separately by three
different illumination units with three different speckle reduction
means.

[0067]Only one sweeping, rotating, vibrating or shaking deflection device
is needed in order to reduce interference pattern on three wavelengths.

[0068]In the following some further basic aspects are elucidated.

[0069]The present invention inter alia also relates to a projection
apparatus as an image generating apparatus using laser light sources as
such.

[0070]The invention describes the optical part of a projection system
using lasers as light sources. Laser illuminated projectors usually
generate inhomogeneous and noisy pictures due to the coherent nature of
laser light. The inhomogeneity is caused by interferences at optical
surfaces within the optical part and the "noise"--usually called
(subjective) speckle--appears at the retina of the observers eye and is
generated by interferences at the diffusing screen.

[0071]An apparatus is presented which solves the problem of inhomogeneity
and reduces the speckle phenomenon.

[0072]Laser projectors are known which use a single laser beam for each
colour (R, G, B) which scans line by line across the screen. The image is
generated on the screen by modulating the beam intensity synchronously
with the beam's position on the screen. Tilting mirrors are used to
deflect the beam in the horizontal and vertical direction.

[0073]Also known are laser projectors using the GLV (Grating Light Valve)
technology. In such devices the laser beam is expanded into a vertical
line which illuminates a 1-dimensional image modulator (GLV chip). The
GLV chip modulates the intensity of the reflected light in order to
generate a vertical line image. The vertical line image is deflected into
the horizontal direction by use of a rotating mirror. A full image is
generated by changing the vertical line image content of the GLV chip
synchronously with the line's horizontal position on the screen.

[0074]A granulated pattern called "speckle" is observed, when laser light
is scattered by a diffusing surface. This phenomenon is caused by the
coherence of laser light. The speckle phenomenon is described in "J. W.
Goodman, J. Opt. Soc. Am, Vol. 66, No. 11, November 1976". Goodman
describes also ways to suppress speckle.

[0075]It is known that laser speckle can be reduced by the presence of a
moving random diffuser or random phase retarder in the optical path, at a
point where the laser is focused before the image formation device or at
a plane where the image is formed in the optical systems. (see Trisnadi
in Proc SPIE 4657, 2002).

[0076]Laser illuminated projectors generate inhomogeneous and noisy
pictures due to the coherent nature of laser light.

[0077]The inhomogeneity--which we also call "objective speckle"--is caused
by interferences of coherent light at rough surfaces, surface
imperfections and aperture stops within the optical system. The speckle
pattern appearing on the screen is independent from the viewing
conditions of the observer, e.g. it is independent from position, viewing
angle or pupil size of the observer.

[0078]The noise--which we also call "subjective speckle"--is caused by
interference of coherent light with the rough surface or with the
diffusing particles of a screen. Coherent light is interfering
constructively or destructively when it is scattered into different
directions, thereby generating a granulated speckle pattern in the image
plane of the observer (e.g. retina of the human eye). The speckle pattern
changes ("moves") when the position or viewing angle of the observer is
changed.

[0079]The present invention describes the conditions of an optical set-up
which reduces both objective and subjective speckle.

[0081]As shown in the Figs, and in particular in FIGS. 1 and 2, a laser
beam l or a set of multiple coincident laser beams or an array of laser
beams is deflected, e.g. by use of a mechanically tilting mirror 11, in
order to sweep across an intermediate surface S which is located within
the illumination unit 20 of a projector I as an image generating
apparatus in the sense of the present invention. The beam l can sweep in
a circular manner or in a linear manner or any other trajectory T across
the intermediate face or surface S. The motion pattern can repeat
cyclically or it can sweep chaotically. Optionally a diffuser 22 can be
used to blur the laser spot for better uniformity.

[0082]An image I of the intermediate surface S is formed in the vicinity
of the aperture stop AS of the projection lens 42, because S and AS are
conjugate to each other.

[0084]The image I is projected in the usual way by means of a projection
lens onto the screen.

[0085]For each received light beam lj according to the sweeping process a
series of beamlets Bi is generated. Each beamlet Bi emerging from
the projection lens 42 creates a specific speckle pattern on the retina
of the observers eye.

[0086]A certain minimal angular separation Δmin between each
two beamlets Bm, Bn is required to make sure that the speckle
patterns created by each beamlet are uncorrelated to each other.

[0087]The value for Δmin depends on the wavelength bandwidth,
the type of screen, the distance between observer and screen and the size
of the pupil of the observer. A typical value found experimentally is
Δmin≈0.5ΘEye. But other values might be
found depending on the specific conditions (bandwidth, . . . ).

[0088]Due to the limitation of Δmin only a limited number of N
uncorrelated beamlets can fill the projection cone angle
ΘProj.

[0089]The beamlets Bi, i=[1, . . . N], are incoherent with respect to
each other as they exist (appear) at disjunct times.

[0090]As the speckle pattern created by the beamlets are uncorrelated with
respect to each other (condition of Δmin) and the beamlets are
incoherent to each other (disjunct times), the superposition of all
individual beamlets leads to a pattern with speckle contrast reduced by
factor N.

[0091]Integrator plates 24-1, 24-2 may be used in the illumination part 20
of the projectors I in order to illuminate the image modulator 31
homogeneously and with rectangular shape.

[0092]The laser beam l or a set of multiple coincident laser beams or an
array of laser beams is swept across a collimation lens 23-1 in such a
way that the active area of a 1st integrator plate 24-1 is partially
or entirely covered. An optional diffuser 22 at any position before a
1st integrator plate 24-1 can be used to blur the laser spot and to
improve the uniformity.

[0093]A 2nd integrator plate 24-2 may be used in conjugate position
to the aperture stop 41, AS of the projection lens 42. As a result light
sweeps in a similar (but inverted) way across the aperture stop 41, AS
like it seeps across the 2nd integrator plate 24-2.

[0094]Light pipe illumination with a light pipe 25 may be used in order to
illuminate the image modulator 31 homogeneously and with rectangular
shape.

[0095]The laser beam l or a set of multiple coincident laser beams or an
array of laser beams is swept across the entrance of the light pipe 25 in
such a way that the entrance area is partially or entirely covered. An
optional diffuser 22 in front of the light pipe 25 can be used to blur
the laser spot and to improve the uniformity. The exit surface of the
light pipe 25 is imaged by a relay lens 23-3 to the image modulator 31.
The relay lens 23-3 may be in conjugate position to the aperture stop 41,
AS of the projection lens 42. As a result light sweeps in a similar but
inverted way across the aperture stop 41, AS like it seeps across the
relay lens 23-3.

[0096]Due to the multiple internal reflections inside the light pipe 25
the light trajectory T of the light spot across the relay lens 23-2 is
different to the trajectory of the light spot across the entrance of the
light pipe 25.

[0098]It can be realized by a diffractive optical element of by a
refractive element with a micro-structured surface and is known from
prior art.

[0099]A rectangular-beam diffuser 22-1 is used to illuminate the image
modulator 31 homogeneously and with rectangular shape.

[0100]A laser beam l or a set of multiple coincident laser beams or an
array of laser beams is swept across the rectangular-beam diffuser 22-1
in such a way that it is partially or entirely covered. The
rectangular-beam diffuser is in conjugate position to the aperture stop
AS of the projection lens. As a result light sweeps in a similar (but
inverted) way across the aperture stop like it seeps across the
rectangular-beam diffuser.

[0101]A laser beam array or a laser beam l with linear cross section or a
set of multiple coincident lasers of that kind may be focussed by a lens
or alternatively a cylindrical lens 52 with axis perpendicular to the
linear laser line onto a mirror 11 which is rotating about an axis which
is parallel to the linear laser line. The rotation axis lies in the
mirror plane.

[0102]The mirror 11 is rotating about that axis a few degrees from left to
right, thereby sweeping the linear shaped laser beam across the 1st
integrator plate 24-1.

[0103]Optionally a diffuser 22 can be placed at any position before the
1st integrator plate 24-1 in order to improve the uniformity.

[0104]A laser beam l or a set of multiple coincident laser beams or an
array of laser beams may be focussed by a lens onto a mirror 11 which is
rotating about an axis, which is going through the centre of the mirror
11. The axis is tilted by a few degrees from the normal axis of the
mirror plane, thereby wobbling the mirror when rotated about the axis and
deflecting the laser beam along a tapered surface. The geometrical
dimensions are adapted in order that the surface of the 1st
integrator plate 24-1 is partially or completely covered by the
circulating laser beam l. An optional diffuser 22 can be placed
preferably between the mirror 11 and the collimation lens 23-1 in order
to blur the laser spot and to cover the 1st integrator 24-1 in a
more uniform way.

[0105]The present invention according to one aspect integrates laser light
sources into known optical illumination architectures of micro-display
type projectors.

[0106]The present invention inter alia also relates to an image generating
apparatus 1 which comprises an illumination unit 20 having an
intermediate face 21, S, as well as an image modulator 30 for generating
an image I. In addition a deflecting means 10 for deflecting a received
light beam I of primary illumination light L1 to said illumination unit
20 is provided in order to irradiate said intermediate face 21, S. Said
deflecting means 10 is adapted to have--during the process of irradiating
said intermediate face 21, S--said light beam l subsequently in time
irradiate different portions of said intermediate face 21, S in order to
thereby reduce the speckle effect.

[0107]According to certain embodiments of the present invention the
following aspects may be essential for an projection type image
generating apparatus, namely the provision of: [0108]an image
generating panel, [0109]a projection lens, which projects the image
displayed on the panel onto a screen, [0110]a light source, which
illuminates the panel, and [0111]an illumination optical means, which
modify the beam of the light source in order to illuminate the panel
uniformly and with a beam shape congruent to the shape of the panel
(generally rectangular shaped).

[0112]According to certain embodiments of the present invention essential
means to be provided and measures to be taken for speckle reduction of an
image generating apparatus using laser light may be based on the
following:

[0113]Each Projection lens or optics PJ has a pupil with a certain
diameter. This diameter together with the distance to the screen defines
a maximum cone angle of a projected point. This cone angle of a projected
point is essential for speckle reduction, if it is ensured that light at
any two locations within this cone is incoherent to each other. In case
of laser light sources such incoherency can be achieved, if a laser beam
is sweeping across the pupil, thereby covering the entire area of the
pupil within a certain time. This ensures that light at any two locations
within the pupil cannot interfere with each other, as light doesn't exist
at any two locations at the same point of time.

[0114]According to certain embodiments of the present invention
illumination optics in a projection apparatus may have an intermediate
surface S which is in conjugate position to the pupil of the lens. The
term optical conjugation means that any location of the pupil is
one-to-one mapped to a location in the intermediate surface S. As a
result, a laser beam sweeping across the intermediate surface S is also
sweeping across the pupil of the projection lens.

[0115]On the other hand, key features of other aspects of embodiments of
the present invention can be summarized as follows: For speckle reduction
it is--in these cases essential--to have (a) a suitable large cone angle
and (b) incoherence of the light forming and projecting the images to be
displayed.

[0116]Property (a) can be achieved by appropriately choosing and setting
the finite size of the aperture stop with respect and in relation to the
finite distance between the aperture stop and the intermediate face.

[0117]Property (b) can be achieved by employing the sweeping process of
the used light beam with respect to the intermediate face.

[0118]According to certain embodiments of the present invention one or a
plurality of the following aspects may be essential for a projection type
image generating apparatus s: [0119]Three image generating panels, each
for displaying an image in the primary colors red, green and blue
respectively. [0120]Three laser light sources, emitting light of primary
colors red, green and blue respective. [0121]Laser beams of all three
light sources converging--at common or different angles of incidence--to
a common point or region at the sweep mirror and being reflected by the
sweep mirror into common or different directions, dependent on the angle
of incidence. [0122]By tilting the sweep mirror in one or two dimensions,
the reflected laser beams are sweeping across common or different
intermediate surfaces of illumination units. [0123]The illumination
unit(s) being adapted in order to illuminate the red, green and blue
image panels with red, green and blue laser light respectively.
[0124]Means for combining the light from the red, green and blue image
panel into a common light path. [0125]A projection lens for projecting
the image of the image panels onto a screen.

[0126]According to FIGS. 4A to 4C, one or a plurality of the following
aspects may be essential for an projection type image generating
apparatus: [0127]Three image generating panels, each for displaying an
image in the primary colors red, green and blue respectively. [0128]Three
laser light sources, emitting light of primary colors red, green and blue
respective. Two laser light sources (e.g. blue and green) combined into a
common optical path. [0129]The common optical path of the two laser light
sources (e.g. blue and green) and the single optical path of the
remaining laser light source (e.g. red) converging under different angles
of incidence at a common point of the sweep mirror and being reflected
into two different directions, dependent on the angle of incidence.
[0130]By tilting the sweep mirror in one or two dimensions, the reflected
laser beams are sweeping across two different intermediate surfaces of
illumination units, one common illumination unit for the common optical
path (e.g. blue and green) and one illumination unit for the single
optical path (e.g. red). [0131]The common illumination unit being adapted
in order to illuminate both panels of the common path colors and a
dichroic beam splitter in order to split the common light path after the
common illumination unit into the single colors (e.g. blue and green).
[0132]The single illumination being adapted in order to illuminate the
panel of the single path color. [0133]X-Cube (also called cross-prism)
for combining the light from the red, green and blue image panel into a
common light path. [0134]A projection lens for projecting the image of
the image panels onto a screen.

[0137]FIG. 1 is a schematical block diagram for elucidating basic aspects
of an embodiment of an image generating apparatus 1 according to the
present invention.

[0138]In FIG. 1 the embodiment of the image generating apparatus 1
according to the present invention comprises means 50 for generating
primary illumination light L1. Said primary illumination light L1 is
generated by one or a plurality of laser light sources 51 or other light
sources which are capable of at least in part producing primary
illumination light L1 which can have a coherence property. One or a
plurality of light beams l are generated. Said primary illumination light
L1 is generated, directed, and focused to a means 10 for deflecting said
primary illumination light L1. Said means 10 for deflecting comprises at
least one deflecting element 11. Said deflecting element 11 can be e.g. a
mirror or any other deflecting entity, for instance a diffraction grating
or the like. Said means 10 for deflecting and said deflecting element 11
are adapted in order to and comprise means for changing the orientational
relationship of the reflection face, interface, surface, or plane of said
reflecting element 11 when compared to the orientation and direction of
the incident light beam l of the primary illumination light L1 in time.
Consequently, said means 10 for deflecting is capable of having said
incident light beam l of said primary illumination light L1 left said
means 10 for deflecting after reflection under temporally changing angle
or orientational relation or direction. Consequently, said means 10 for
deflecting and said deflection element 11 are adapted to have the
deflected light beam l of primary illumination light L1 move around
either continuously or by jumping to and/or between a discrete set of
angular positions or orientations.

[0139]The deflection of said means 10 for deflecting and of said
deflecting element 11 are controlled and chosen in order to have said
light beam l of primary illumination light L1 irradiate different
positions and/or portions of an illumination unit 20 as means 20 for
illuminating an image generation device 30 as in means 30 for generating
an image and in particular an intermediate face, surface, interface, or
plane 21, S comprised in said illumination unit 20 or means 20 for
illuminating.

[0140]As in illumination unit 20 said means 20 for illuminating may
comprise further optical elements such as collimation lenses 23-1,
condenser lenses 23-2 and some light integration/integrator means 24-1,
24-2. The light beam l of incident primary illumination light L1 is
therefore modified and temporally split up into a bundle of beamlets
Bj which for each instant of time generate an image, however, based
on different irradiated portions of the intermediate face 21, S of said
illumination unit 20.

[0141]The speckle pattern generated by the beamlets are uncorrelated to
each other as long as the lateral distance between each beamlet is
sufficiently large. Additionally, the light of the beamlets is incoherent
to each other as it does not exist at the same point in time. Therefore,
the individual speckle pattern generated by each beamlet superimpose on
intensity basis, thereby reducing the speckle contrast of the
superimposed image.

[0142]In FIG. 1 a diffusing screen or face 22, S' is also shown. Such a
diffusing screen 22, S' may be used to further increase uniformity.

[0143]After interaction with the illumination unit the incident primary
illumination light L1 leaves the illumination unit 20 as secondary
illumination light L2 in order to be directed to means 30 for image
generation which comprises an image modulator 31, e.g. an LCD element
which can be operated in transmission or in reflection.

[0144]After interaction with said means 30 for image generation and in
particular with said image modulator 31 said incident secondary
illumination light L2 leaves said image generating means 30 as tertiary
imaging light L3 in order to be directed to the following image
projection means 40 or respective projection optics 40 which embodiment
of FIG. 1 comprises a projection lens 42 with its aperture stop 41, AS in
order to generate from said incident tertiary imaging light L3 projection
light as L3' conveying the image I to be projected to a screen and/or to
an observer's eye.

[0145]FIG. 2 is a schematical and perspective side view of another
embodiment of an image generation apparatus 1 according to the present
invention.

[0146]Again means 10 for deflecting a beam l of primary illumination light
L1, an illumination unit 20 having an intermediate surface S, 21 and
optional a diffuser screen 22, S', means 30 for generating an image I
having an image modulator 31, and means 40 for projecting said image I as
a projected image I' having an aperture stop AS, 41 and a projection lens
42 are provided which are positioned in a common optical path in this
order in the direction of light propagation, i.e. from left to right in
FIG. 2. In addition, FIG. 2 indicates that the intermediate face S, 21
and the face of the aperture stop AS, 41 are in optical conjugation with
respect to each other, i.e. each portion irradiated on said intermediate
face S, 21 is imaged on a respective portion of the face of the aperture
stop AS, 41.

[0147]FIG. 3 is a schematical top view for elucidating properties of an
image generating apparatus 1 according to the present invention. Here the
principles of FIGS. 1 and 2 are included, in particular with respect to a
plurality of received light beams l1 and l2.

[0148]The embodiment shown in FIG. 3 comprises two image generating
optical paths P1, P2 and P3 which are adapted to receive primary
illumination light L1 and for generating respective partial images I1, I2
and I3 which may after their generation be combined to give an combined
image I to be displayed or to be projected.

[0149]The light sources 51-1 and 51-2 are combined into one common path
(P1+P2) before focused to mirror 11 and split after the illumination unit
20-1 by use of a dichroic mirror 60 into separate paths P1 and P2 in
order to illuminate image panel 30-1 with light 11 and 30-2 with light
12.

[0150]For generating light beams l1, l2 and l3 of primary illumination
light L1 and having distinct and different spectral properties light
generating means 50 comprising a first light source 51-1, a second light
source 51-2 and a third light source 51-3 is provided. The light sources
51-1, 51-2 and 51-3 are adapted and arranged in order to direct and focus
respective light beams l1, l2 and l3 of primary illumination light L1 to
a central portion of a mirror element 11 which is comprised in or which
forms a single and common means 10 for simultaneously receiving and
deflecting the plurality of light beams l1, l2 and l3 from said light
sources 51-1, 51-2 and 51-3 to said image generating optical paths P1, P2
and P3 in order to irradiate the same or at least respective intermediate
faces 21-1, S1; 21-2, S2 contained therein within respective means 20-1,
20-2 for illuminating which may also referred to as illumination units
20-1, 20-2.

[0151]It is an aspect of the embodiment shown in FIG. 3 that only one,
i.e. a single deflecting means 10 is necessary in order to receive and
deflect the plurality of light beams l1, l2 and l3 of primary
illumination light to the respectively assigned optical paths P1. P2 and
P3. Therefore, the assignment between the light sources 51-1, 51-2 and
51-3 the respective light beams l1, l2 and l3 and the optical paths P1
and P2 and its intermediate faces 21-1, S1; 21-2, S2 is realized by
optical and geometrical means.

[0152]When using a reflecting element 11, for instance a mirror or the
like as a part of said deflecting means 10, the distance D and the
orientation between the image generating optical paths P1 and P2 as well
as the position--e.g. the distance d and the orientation--of said single
and common deflecting means 10 with respect to the image generating
optical paths P1 and P2 are chosen such that by taking into account the
fact that the law of reflection is fulfilled at the reflecting interface
of the mirror 11 the first light beam l1 which is incident at an angle
α is reflected at an identical reflection angle α' towards
the assigned first image generating optical path P1, whereas the second
light beam l2 which is incident at an angle β is reflected at an
identical angle of reflection β' towards said assigned second image
generating optical path P2.

[0153]Therefore, the crucial point is the arrangement of the image
generating optical paths P1 and P2 with respect to the reflecting element
11 or the mirror 11 in connection with the position and orientation of
the said first and second light source 51-1 and 51-2.

[0154]Of course, instead of a single light source 51-1 a combined light
source might be used which irradiates as a first light beam l1 a
plurality of spectral components at the same angle of incidence α.

[0155]This aspect is demonstrated in the embodiment as shown in FIG. 4A.
Here, one light beam actually is a combined light beam comprising two
colors, i.e. two different spectral components and therefore two light
beams l1 and l2 in combination, whereas the other light beam l3 as a
third light beam l3 conveys a single color only.

[0156]By using a common first collimation lens 23-1 said deflected first
and second light beams l1 and l2 and said third light beam l3 are
irradiated and collimated into the first and second optical paths P1 and
P2, respectively. Therefore, said first and second light beams l1 and l2
use a common first illumination optical path P1. The third light beam l3
uses the other second illumination optical path P2.

[0157]A first component of each optical path P1 and P2 is inter alia
formed by the mentioned means 20-1, 20-2 for illuminating which are also
called illumination units 20-1 and 20-2, respectively. Each illumination
unit 20-1, 20-2 may comprise first and second integrator plates 24-1 and
24-2 as well as a condenser lens 23-2.

[0158]After the condenser lens 23-2 said first and said second light beam
l1 and l2 leave their common first illumination unit 20-1, said third
light beam l3 leaves the respective second illumination unit 20-2.

[0159]Said first and second light beams l1, l2--as a combined beam
l1+l2--are then subjected to color separation by interacting with a
spectral selective mirror or dichroic mirror 60 spectrally subdividing or
separating the combined first and second light beams or laser beams l1,
l2 into a separate first colored light beam l1 and into a separate second
colored light beam l2. The first colored light beam l1 conveying the
first color transmits said dichroic mirror 60, is not deflected and
enters a first polarization selective beam splitting cube PBS1. The
second colored light beam l2 is deflected by 90° and enters a
second provided polarization selective beam splitting cube PBS2.

[0162]In each case after having entered the respective polarization
selective beam splitting cube PBSj each light beam lj is deflected by
90° at the polarization selective interface of each polarization
selective beam splitting cube PBSj in order to leave the respective
polarization selective beam splitting cube PBSj and in order to enter a
reflective image modulator 31-1, 31-2, 31-3 in the form of a respective
reflective liquid crystal display LCD1, LCD2, LCD3 being comprised in
respective first, second, and third means 30-1, 30-2, and 30-3, for image
generation, respectively.

[0163]After being reflected at each of said liquid crystal displays LCDj,
j=1, 2, 3 the polarization state of each reflected beam l1, l2, l3--now
conveying a respect first, second and third colored partial image I1, I2,
I3, respectively--has been partially changed, dependent on the image
content on the reflective liquid display panels: Light from bright areas
of each image have changed polarization state and travel through the
polarization selective beam splitting cubes PBSj, whereas light from dark
areas of each image--having not changed the polarization state--is being
reflected at the polarization selective interface.

[0164]Each of the three beams l1, l2, l3 leaves the respective
polarization selective beam splitting cube PBSj in order to enter a color
recombination cube 43 according to the interaction of which the
respective beams convey partial images I1, I2, and I3 each of which
corresponding to the respective three colors are combined by entering
into and interacting with a color recombination cube 43 into a single and
combined image path which conveys a superposition I of said partial
images I1, I2, and I3, which is projected on the screen.

[0165]FIG. 4B is a schematic side view of an embodiment of the image
generating apparatus 1 according to the present invention, wherein a
light pipe is used for illuminating the image modulator 31. Here the
sweeping beam L enters a light input face of the provided light pipe. The
light pipe redistributes and redirects the received light in order to
make the light distribution more homogeneous.

[0166]Instead of using a light pipe, a rectangular beam shaper 22-1 may be
involved as is shown in the embodiment according to FIG. 4C.

[0167]FIG. 5 is a schematical and cross-sectional top view of a known
image generating apparatus 1' again a combination of three polarization
selective beam splitting cubes PBSj, j=1, 2, 3 in connection with three
reflective liquid crystal display devices LCDj, j=1, 2, 3, and a common
color recombination cube 43 are involved.